Self-starting synchronous motor



211 27, 1940. FF R 2,212,222

SELF-STARTING SYNCHRONOUS MOTOR Filed July 19, 1959 j a 1125491" j Patented Aug. 27, 1940 UNITED STATES PATENT OFFICE SELF- STARTING SYNCHRONOUS MOTOR Andreas Lauffer, Schwenningen-on-the-Neckar,

Germany Application July 19, 1939, Serial No. 285,424 In Germany July 28, 1938 Claims. (Cl. 172278) This invention relates to small self-starting, Fig. 3 is an elevational view of another exsingle-phase synchronous motors, more partlcuample. larly for driving clocks or the like, in which in a Fig. 4 is a sectional view taken on the line known manner for enabling the unpolarised rotor 1VIV of Fig. 3. 5 to start there are provided next to the main Fig. 5 shows a motor according to Fig. 2 in 5 poles additional auxiliary poles, the magnetic section, with a modified form of rotor.

flux of which is phase-displaced with respect to The two halves 3 and 4 of the stator are conthe main poles by a short-circuit winding. For nected to the core 2 of the excitation coil i. The obtaining low speed the number of poles of the two halves of the stator are disposed in one plane,

stator is made fairly high. Finding space for the the plates of one half being cut out in circular 10 large number of poles close to one another preform in such a manner that they embrace the sents difiiculties however and results in compliplates of the other stator half. Each half of the cations in the assembling of the stator laminastator consists of two superposed plates 5, 6 tions which have to be given a great number of and 5', 6' respectively, of which the plates 5 and offsets. 5 form the main poles and the plates 6 and 6 15 In the small synchronous motor according to form the auxiliary poles. The plates might be the present invention the halves of the stator still further subdivided, so as to reduce the iron consist each of two plates, one for the main losses. The formation of the poles from a single poles and one for the auxiliary poles, connected plate, however, has the advantage of greater simto the ends of the core of the excitation coil. plicity and stability of the poles. A further sub- 20 According to the invention the plates of one division also involves the danger of the occurstator half contain in a circular opening the rence of noise at the poles. All the stator plates plates lying in the same plane of the other stator have projecting pole pieces which are bent over half. The main and auxiliary poles are bent once at right angles, so that all the auxiliary over, in each case from one plate or the stator poles and all the main poles in each case lie on a 25 halves, in such a manner that the ring of main cylindrical surface. Thus from the stator plate poles and the ring of auxiliary poles are dis- 5 the main poles 9 and from the stator plate 5' posed on two cylindrical surfaces, one or which the other main poles l are bent over. From the embraces the other. In this construction, even stator plate 6 the auxiliary poles I0 and from 80 in a motor of the smallest dimensions, there is the stator plate 6 the auxiliary poles 8 are bent 80 space for any number of poles, the parts of the over. stator consisting of simple plates, out of which In order to give the auxiliary poles a magthe pole teeth are bent over with a single bend. netio flux which is phase-displaced with respect As all the auxiliary poles lie on the same cylinto the main poles, they are provided with an addrical surface, they can be loaded by a common ditional winding, for instance a short-circuiting 35 short-circuiting ring. The rotor which is of ring. In the arrangement according to the inannular shape may rotate between the rings of vention a metal ring H common to all the auxpoles or inside or outside them. For obtaining a iliary poles may however be applied in a very greater torque it may have a plurality of annular simple manner, which ring has corresponding parts which rotate inside, between or outside the openings, through hich th auxiliary poles 40 rings of D This arrangement (106$ 1101? tend. The main poles of course extend past the large the overall dimensions of the motor. The ring The ring is not closed, but has a Slot plates forming the internally disposed half of for the purpose f preventing any mom the stator may carry the bearing for the rotor. enable eddy currents In order further to reduce the dimensions, the The rotor 12 may be made pot shaped or ring 45 free ends of the teeth of the outer 1mg of poles Shaped In any case it has an annular part '3 may be bent Over into the cylindrical surface the diameter of which is such that it will rotate of the inner ring of poles.

I 1 mm Xam 185 of he invem either inside or outside or between the two rings several constructo e p t of poles. The rotor may be made completely '11 trated in the accom a in drawg g i p m g smooth and is preferably made of hardened, but 50 g 1 represents a motor in elevation, the not magnetised steel. Consequently it will act tor being removed, during starting as a Ferraris disc, while during Fig. 2 shows a section of this example on line operation poles are formed in a known manner, 1 f Fig 1. as if'the rotor were polarised. For obtaining a 55 particularly high torque, it may be provided at one face with serrations.

The strongest starting torque is of course obtained when the rotor rotates between the two rings of poles. The torque can however be further increased, by giving the rotor several annular parts, of which one rotates between the rings of poles and the other annular part of annular parts inside or/and outside the ring of poles. A constructional example with three annular parts is shown in Fig. 5. The construction of this motor is for the rest the same as that shown in Figs. 1 and 2. The rotor however has three concentric annular parts l3, I4 and I5; of which the middle annular part I3 rotates between the two rings of poles, the inner annular part I! rotates inside the poles and the part l5 rotates outside the ring of poles.

A particularly flat form of construction of the motor results, when the rotor rotates only inside the ring of poles, as shown in Fig. 4. With the pole pieces constructed as in Figs. 1 and 2, the

auxiliary poles would be at a fairly great distance from the rotor and could thus only produce a weak starting torque. Thus it is preferable,

in the construction of the rotor in a manner as shown in Fig. 4, for the auxiliary poles 8 and ID to be bent over in such a mannerthat they extend into the same cylindrical surface as the main poles I and 9.

The internally disposed stator half 4, which consists of the plates 5' and 6', may at the sametime support the hearing it for the rotor.

What I claim is:

1. A self-starting single-phase synchronous motor comprising in combination a core, an excitation coil on said core; a rotor. a stator having a plurality of main poles and auxiliary poles and consisting of two halves each composed of two plates, the plates of one stator, half being connected to one end of said core and the plates of the other stator half to the other end of the core, the plates of one stator half having an opening for containingvthe plates of the other stator half in the same plane, main poles formed by a ring of teeth bent out of the plane of one plate of each stator half, and the auxiliary poles formed by a ring of teeth bent out of the plane of the other plate of each stator half in such a manner that the ring of main poles and the ring of auxiliary poles are disposed onv two cylindrical surfaces one of which embraces the other.

2. A motor as claimed-in claim 1 and comprising a common ring-shaped short-circuiting element surrounding the teeth of the ring of auxiliary poles.

3. A motor as claimed in claim 1 and in which 

